J. D. Dana on the Recent Eruption of Mauna Loa. Ill 



during the gradual process of fossilization, after the manner 

 of pseudomorphism in minerals, the fluoride of calcium gra- 

 dually replacing the organic matter, as transformation pro- 

 ceeded, than that it should have been an original constituent 

 of the bones of the living animal. Still, the subjoined analyses 

 of the enclosing matrix gives no evidence whatever of the 

 existence of fluorine in these deposits now. 



If the fluorine has really been derived from these deposits, 

 we are forced to the conclusion that it has all been removed 

 by the powers of pseudomorphism. May we not, however, 

 rather look to the saline waters, now common in that coun- 

 try, as the source of the fluorine ; or perhaps, to the waters 

 of the lake, bay, or estuary, in which the bones may have 

 lain macerating, previous to their long interment ? 



It is worthy also of note that Greene's analysis shews the 

 presence of sulphate of baryta in the compact portion of 

 the bone he analysed ; and Dr Genth discovered minute 

 crystals of sulphate of baryta in the cavities of some of the 

 bones by the aid of a stronger magnifier. — (Ovjen's Geolo- 

 gical Survey of Winsconsin, Iowa, and Minnesota.) 



Note on the Eruption of Mauna Loa. By James D. Dana. 

 (Communicated by the Author.) 



The account of Mauna Loa, by Rev. Titus Coan, together 

 with the additional information from letters appended to this 

 paper, suggests a few thoughts confirmatory of views men- 

 tioned in another place by the writer. 



1. The eruption described, although so vast in its extent, 

 commenced with no earthquake — no internal thunderings — 

 no premonitions whatever, that were perceptible at the base 

 of the mountain. In almost all descriptions of volcanoes, 

 these phenomena are set down as essential to the result, 

 especially if the eruption be of much extent. Some force is 

 supposed, in one way or another, to get beneath the column 

 of lava, and by sudden action to eject the lavas with violence, 

 amid terrific exhibitions of volcanic power. But in the 

 majestic dome of Mauna Loa, where the lavas are carried to 



